Acetylenic glycols as corrosion inhibitors



United States Patent 2,993,862 AOETYLENIC GLYCOLS AS CORROSIONINHIBITORS Roger F. Monroe and Fred J. Lowes, Midland, Mich., and GeraldL. Foster and Billy 1).0akes, Tulsa, Okla., assignors to The DowChemical Company, Midland, Mich., a corporation of Delaware No Drawing.Filed Aug. 2, 1956, Ser. No. 601,641

6-Claims. (Cl. 252-146) This invention relates to corrosion inhibitorsfor use in aqueous hydrochloric acid to inhibit the corrosion of iron,steel, nickel or ferrous alloy metals exposed to said aqueous acid.

We have now discovered that certain acetylenic glycols, specifically,those having the formula R R Rd0E0-GE0d-R H H wherein R is a radicalselected from the group consisting of H and CH are potent corrosioninhibitors and, as such, are particularly efiective in protecting iron,steel, [ferrous alloys and nickel from the corrosive attack of aqueoushydrochloric acid. By the term aqueous hydrochloric acid we mean HCl inthe presence of a significant amount of Water and do not mean to excludethe presence of other substances.

According to the invention, the inhibitors are simply dissolved in thehydrochloric acid solution the corrosive action of which is to beinhibited. Only a small amount of inhibitor is required. As little as afew thousandths of .1 percent, based on the acid solution, significantlyreduces the corrosion of iron and nickel exposed to the acid. The degreeif inhibition increases with the concentration of the inhibitor up to aconcentration of about 1 percent. Beyond this point there is littleadvantage in using more inhibitor.

The inhibitors of the invention are efiective not only at ordinarytemperatures but also at elevated temperatures, up to the point at whichthe inhibitors decompose. They are effective in all concentrations ofhydrochloric acid up to and including commercial concentrated acid(about 36 percent). Applications in which they are particularly usefulinclude metal-cleaning baths, oil welltreating acids, boiler-cleaningsolutions and the like.

In order to illustrate the effectiveness of our corrosion inhibitors wehave conducted tests in which hydrochloric acid at variousconcentrations and containing 0.4 percent of the inhibitor being testedis placed in contact with a standard coupon of the metal to beprotected. After 16 hr. the coupon is washed, dried and weighed todetermine the amount of metal dissolved by the acid. From this iscalculated the corrosion rate in terms of inches of penetration peryear. Some typical results thus obtained are shown in Table I.

TABLE I Corrosion rates, inches penetration per year, of steel andnickel exposed to hydrochloric acid Results similar to those shown inTable I were obice Patented July 25, 1961 tained when otherconcentrations of hydrochloric acid, other temperatures in the rangefrom room temperatures up to the decomposition point of the inhibitor,and other ferrous metals were used instead of those used in obtainingthe data in Table I. It was also found that the effectiveness of theinhibitors was not impaired by the presence of liquids other than water,such as, for instance, alcohols, glycols or surfactants. Likewise, theirefiectiveness was not impaired by the presence of various salts in theaqueous acid such as the soluble chlorides and sulfates.

We claim:

1. Aqueous hydrochloric acid containing about 5 to 36% concentration, byweight, and, as the sole active corrosion inhibitor therefor anefiective amount of a compound having the formula H H wherein R is aradical selected from the group consisting of H and --CH 2. A solutionas in claim 1 wherein R is H.

3. A solution as in claim 1 wherein R is CH 4. A solution as in claim 1wherein the concentration of the inhibitor is from a few thousandthspercent to about one percent, by weight.

5; A process for inhibiting the corrosion of a metal of the groupconsisting of iron, steel, nickel and ferrous alloys by aqueoushydrochloric acid in contact therewith comprising maintaining in saidacid a small but effective concentration of the inhibitor having theformula R RJJ- EC -CEO-ER H H wherein R is a radical selected from thegroup consisting of H and CH3.

6. A process as defined in claim 5 wherein the concentration ofinhibitor is from a iew thousandths percent to about 1 percent, byweight.

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1. AQUEOUS HYDROCHLORIC ACID CONTAINING ABOUT 5 TO 36% CONCENTRATION, BYWEIGHT, AND, AS THE SOLE ACTIVE CORROSION INHIBITOR THEREFOR ANEFFECTIVE AMOUNT OF A COMPOUND HAVING THE FORMULA